A plurality of data bits may be encoded as a complex coordinate data point. The encoding may be in the form of quadrature modulation of a carrier signal. A receiver may be configured to demodulate and sample the carrier signal, determine complex coordinates of the samples, and correlate the complex coordinates with points of a reference constellation. Each point of the reference constellation is associated with a unique set of bit values, such that a correlation to a point of the reference constellation provides a corresponding set of decoded bit values. The correlation may include computing a log-likelihood ratio (LLR) for each of plurality of bits of a data point, relative to points of the reference constellation.
A LLR may be computed as a function of distances between complex coordinates of the data point and every point of a reference constellation, in accordance with a full logarithmic maximum-a-posteriori (Full-Log-MAP) LLR technique. A Full-Log-MAP technique may be relatively expensive to implement in terms of processing time and resource consumption.
Where a Log-MAP function utilizes distances to less than all points of a reference constellation, decoding performance may be adversely affected.
In the drawings, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears.